Analysis of gaseous mixtures

ABSTRACT

A gaseous mixture containing nitrogen, carbon monoxide, carbon dioxide, hydrogen, water vapor and hydrocarbons is analyzed by injecting a sample of the mixture into a carrier gas. The carrier gas containing the sample is passed through a body of crosslinked organic polymer which retards passage of the water vapor while permitting passage of other constituents. The effluent from the body of polymer is directed to a chromatographic analyzer which contains a molecular sieve adsorbent. The body of polymer is maintained at a temperature sufficiently high to prevent condensation of the water vapor.

United States Patent Temple et al.

[45] Mar. 21, 1972 [54] ANALYSIS OF GASEOUS MIXTURES [72] Inventors:Harry F. Temple; Robert L. Thomas, both of Bartlesville, Okla.

[52] U.S. Cl ..55/31, 55/67, 55/68, 55/75, 73/231 [51] Int. Cl ...B0ld53/04, GOln 31/08 [58] Field of Search ..55/33, 35,62,67, 68, 75,55/197, 386, 32; 73/231 [56] References Cited UNITED STATES PATENTS3,357,158 12/1967 Hollis ..55/67 3,242,651 3/1966 Arnoldi ..55/623,359,707 12/1967 Jean ..55/33 3,038,326 6/1962 De Ford ....55/673,490,202 l/ 1970 Ayers ..55/67 Primary Examiner-Charles N. HartAttorney-Young and Quigg [5 7] ABSTRACT A gaseous mixture containingnitrogen, carbon monoxide, carbon dioxide, hydrogen, water vapor andhydrocarbons is analyzed by injecting a sample of the mixture into acarrier gas. The carrier gas containing the sample is passed through abody of cross-linked organic polymer which retards passage of 6 Claims,2 Drawing Figures GASES FEED CARBON BLACK REACTOR ll l4 FUELj k l3 l7:SEPARATION l L CARBoN BLACK 16 PATENIEDMARZ] I972- IIO CARBON BLACKREACTOR FEED] FILTER fZI FUELj k 2 |3 CARRIER GAS ANALYZER INVENTORS H.F. TEMPLE R. L. THOMAS A 7' TORNEYS ANALYSIS OF GASEOUS MIXTURES In manyindustrial operations there is a need to analyze gaseous mixtures of lowmolecular weight constituents. For example, it is desirable to analyzethe effluent stream from a carbon black reactor to determine operatingconditions. The gases in such a stream include nitrogen, carbonmonoxide, carbon dioxide, water vapor and small quantities of varioushydrocarbons. While many gaseous-mixtures can readily be analyzed bymeans of chromatography, considerable difficulty is encountered inanalyzing mixtures of the type described.

In accordance with this invention, an improved method is provided foranalyzing fluid mixtures of the type described. The actual analysis ismade by a conventional chromatographic analyzer which contains amolecular sieve adsorbent. Carrier gas having a sample of the mixture tobe analyzed is first passed through a body of material which is capableof selectively removing the water vapor. This material is a crosslinked,finely divided, microporous organic polymer of the type hereinafterdescribed in detail. The polymer is maintained at a temperaturesufficiently high to prevent condensation of the water vapor. Suchpolymer retards passage of water while permitting passage of certain ofthe low molecular weight gases.

In the accompanying drawing,

FIG. 1 is a schematic representation of carbon black producing apparatushaving an analyzer constructed in accordance with this inventionassociated therewith.

FIG. 2 is a schematic representation of apparatus capable of carryingout the method of this invention.

Referring now to the drawing in detail and to FIG. 1 in particular,there is shown a conventional carbon black reactor 10. A feed stream,such as an aromatic oil, is introduced through a conduit 11. Fuel andair are introduced through respective conduits 12 and 13. The effluentfrom the reactor is removed through a conduit 14 and passed toseparation facilities, from which carbon black is removed through aconduit 16 and effluent gases are removed through a conduit 17. In orderto determine proper operating conditions of the reactor, it is desirableto analyze the gasesin the effluent stream from the reactor. This isaccomplished by withdrawing through a conduit 18 a sample of the reactoreffluent. A filter 19 removes solid particles. The effluent from thefilter is passed through a conduit 20 to an analyzer 21 which isconstructed to perform the analysis method of this invention.

Analyzer 21 is illustrated schematically in FIG. 2. The analyzerincludes a conventional chromatographic column 22 which is filled with apartitioning material capable of separating certain constituents of thegaseous mixture to be analyzed. A molecular sieve material, such as asynthetic zeolite, is employed as the separating material in column 22.The analyzer of FIG. 2 includes second and third columns 23 and 24 whichare filled with organic polymers of the type to be described. Thepurpose of column 23 is to remove water vapor from the sample. Thepurpose of column 24 is to retard passage of carbon dioxide andacetylene while permitting passage of other constituents. The analyzerincludes three stream switching valves 25, 26 and 27. Valve 25 isprovided with six ports 25a, 25b, 25c, 25d, 25c and 25f. When the valveis in a first position, the individual ports are connected in the mannerillustrated by the solid lines. When the valve is in a second position,the individual ports are connected in the manner shown by the brokenlines. Conventional rotary or diaphragm operated chromatographicanalyzer sample valves well known in the art can be employed as valve25. Valves 26 and 27 are of corresponding structure.

The gaseous sample to be analyzed is introduced through conduit 20 whichcommunicates with port 25a. A valve 28 is disposed in conduit 20. Asample loop 30 of predetermined volume communicates between ports 25cand 25f. A vent conduit 31 is connected to port 25b. A conduit 32extends between port 25e and port 26a of valve 26. Carrier gas, such ashelium, is introduced into the system through a conduit 30 whichcommunicates with port 25d. A conduit 34, which has a valve therein,extends between conduit 33 and port 25d.

Column 24 and a detector 36 are connected between ports 26b and 27a.Column 22 is connected between ports 27 and 27f. A conduit 37 extendsbetween port 27d and the inlet of a detector 38. A conduit 39, which hasa valve 40 therein, communicates between ports 27b and 27c.

As previously mentioned, columns 23 and 24 are filled with crossJinked,finely divided, microporous organic copolymer. This copolymer is formedby polymerizing at least 20 percent by weight of at least one divinylmonomer selected from monocyclic divinyl aromatic hydrocarbons andethylene glycol dimethacrylate and not more than percent by weight of atleast one monoethylenically unsaturated monomer copolymerizabletherewith selected from monocyclic monovi nyl aromatic hydrocarbons,N-vinyl pyridine and N-vinyl pyrrolidone. These copolymers usually havea surface area of at least 50 square meters per gram and particle sizesbetween 5 and 500 microns. Copolymers of this type are availablecommercially from Waters Associates, Inc. of Fanningham, Massachusetts,under the trademark Porapak." These copolymers can be produced by theprocedures and using the monomers described in US. Pat. No. 3,357,158.Column 22 contains a molecular sieve adsorbent material. In one specificembodiment of this invention column 23 was a 30 inch long tube filledwith Porapak R. Column 24 was a 4 feet long tube filled with Porapak Q.Column 22 was a 6 feet long tube filled with 13X molecular sievematerial.

The effluent gases from reactor 10 contain nitrogen, carbon monoxide,carbon dioxide, hydrogen, water vapor and small amounts of varioushydrocarbons. The stream removed through conduit 18 is maintained at atemperature sufficiently high to prevent condensation of water vaporbefore the sample enters column 22. To this end, column 23 is maintainedat a temperature sufficiently high to prevent condensation. Atemperature of about 350 F. is quite effective for this purpose. Such atemperature can be maintained by wrapping the column around a metalmandrel which has a heating element embedded therein. A thermostat cancontrol the current to the heating element. The mandrel and column canbe posi tioned within an insulated housing.

In the operation of the apparatus illustrated in FIG. 2, valves 25,26and 27 initially occupy the first mentioned positions wherein theindividual ports are connected by the solid lines. The sample to beanalyzed flows through sample loop 30 and is vented through conduit 31.Carrier gas enters through conduit 33 and flows through columns 23, 24and 22. This initial flow of carrier gas purges the columns of anyconstituents remaining from prior analyses. Valve 41 can be closed atthis time to prevent loss of carrier gas through conduit 42. When it isdesired to perform an analysis, valve 25 is actuated to the secondposition so that the ports are connected in the manner illustrated bythe broken lines. Immediately prior to this time valve 28 is closed todiscontinue the sample flow. Carn'er gas from conduit 33 flows throughsample loop 30 after valve 25 is actuated so as to displace the sampleoriginally trapped in the loop. After the sample has been displaced fromloop 30, valve 25 is returned to its initial position. The sampledisplaced from loop 30 is introduced into column 23, which in theembodiment described is maintained at a temperature of approximately 350F.

The constituents, other than water, of the sample displaced from loop 30flow through column 23 in a matter of a few seconds. The actual timerequired can readily be determined experimentally for a given samplebyconnecting a detector to the outlet of the column. The water initiallypresent in the sample is retained on the packing material of column 23.When the remainder of the sample has passed through column 23, valve 26is actuated so that ports are connected as illustrated by the brokenlines. Valve 41 is opened at this same time. Carrier gas flows throughcolumn 23 in the opposite direction at this time to back-flush thecolumn, with the effluent being vented through conduit 42. During thetime that column 23 is being back-flushed, carrier gas from conduit 34passes through column 24 to continue the flow of sample through columns24 and 22. After a sufficient period of time has elapsed to back-flushcolumn 23, valve 26 is returned to its initial position. Valve 35permits adjustment of the rate of flow of carrier gas through conduit34.

The packing material in column 24 serves to retard selectivelythepassage of carbon dioxide and acetylene while permitting the remainingconstituents to pass into column 22. While column 23 also retards theconstituents to some degree, they are passed more freely than water sothat there is essentially no loss in column 23. Detector 36 provides anindication of the flow of the remaining light gases to column 22. Whenthese gases have passed through the detector into column 22, valve 27 isactuated to direct the effluent from column 24 directly to detector 38for measurement. After the carbon dioxide and acetylene peaks have beenread, valve 27 is returned to its initial position to direct carrierfluid through column 22 and thereby elute the remaining light gasconstituents into detector 38 to complete the analysis. Valve 40 permitsthe flow to detector 38 to be regulated when the effluent from column 24is passed to this detector.

It is important to prevent water vapor from entering column 22 becausewater rapidly destroys the separating ability of the molecular sieveadsorbent. It is also important to maintain the carrier gas water-free.Column 24 is employed to advantage because carbon dioxide does notreadily pass through the material in column 22.

While the invention is particularly useful in analyzing gases in theeffluent from a carbon black reactor, the invention can be employed inanalyzing light gases from other types of combustion process whereinwater vapor is present. While the invention has been described inconjunction with presently preferred embodiments, it obviously is notlimited thereto.

We claim:

I. The method of analyzing the effluent gases from a carbon blackreactor, which method comprises:

filtering a sample of the effluent gases to remove solid particles andthereby obtain a gaseous mixture;

introducing said gaseous mixture into a stream of carrier passing theresulting mixture of sample and carrier gas through a first zonecontaining a cross-linked, finely divided, microporous organic copolymerof l) at least percent by weight of at least one divinyl monomerselected from the group consisting of monocyclic divinyl aromatichydrocarbons and ethylene glycol dimethacrylate, and (2) not more thanpercent by weight of at least one monoethylenically unsaturated monomercopolymerizable therewith selected from the group consisting ofmonocyclic monovinyl aromatic hydrocarbons, N-vinyl pyridine and N-vinylpyrrolidone; maintaining said first zone at a temperature sufficientlyhigh to prevent condensation of water vapor;

discontinuing the passage of said sample through said first zone beforewater vapor appears in the eflluent from said first zone;

passing the effluent from said first zone through a chromatographiccolumn to a detector; and

passing the effluent from said chromatographic column to a detector tomeasure constituents of said gaseous mixture as they emerge from saidchromatographic column.

2. The method of claim 1 wherein said first zone is maintained at atemperature of about 350 F.

3. The method of claim 1, further comprising the step of passing a purgegas through said first zone in a direction opposite to the directionsaid mixture is passed through said first zone, said purge gas being sopassed after the passage of said mixture is discontinued so as to removewater vapor from said first zone.

4. The method of claim 1 wherein the effluent from said first zone ispassed through a second zone prior to passage through saidchromatographic column, said second zone containing a material thatselectively retards passage of carbon dioxide and acetylene, and passingcarbon dioxide and acetylene from said second zone to a detector.

5. The method of claim 4 wherein said second zone contains across-linked, finely divided, microporous organic copolymer of (1) of atleast 20 percent by weight of at least one divinyl monomer selected fromthe group consisting of monocyclic divinyl aromatic hydrocarbons andethylene glycol dimethacrylate, and (2) not more than 80 percent byweight of at least one monoethylenically unsaturated monomercopolymerizable therewith selected from the group consisting ofmonocyclic monovinyl aromatic hydrocarbons, N-vinyl pyridine and N-vinylpyrrolidone.

6. The method of claim 1 wherein said chromatographic column contains amolecular sieve adsorbent.

2. The method of claim 1 wherein said first zone is maintained at atemperature of about 350* F.
 3. The method of claim 1, furthercomprising the step of passing a purge gas through said first zone in adirection opposite to the direction said mixture is passed through saidfirst zone, said purge gas being so passed after the passage of saidmixture is discontinued so as to remove water vapor from said firstzone.
 4. The method of claim 1 wherein the effluent from said first zoneis passed through a second zone prior to passage through saidchromatographic column, said second zone containing a material thatselectively retards passage of carbon dioxide and acetylene, and passingcarbon dioxide and acetylene from said second zone to a detector.
 5. Themethod of claim 4 wherein said second zone contains a cross-linked,finely divided, microporous organic copolymer of (1) of at least 20percent by weight of at least one divinyl monomer selected from thegroup consisting of monocyclic divinyl aromatic hydrocarbons andethylene glycol dimethacrylate, and (2) not more than 80 percent byweight of at least one monoethylenically unsaturated monomercopolymerizable therewith selected from the group consisting ofmonocyclic monovinyl aromatic hydrocarbons, N-vinyl pyridine and N-vinylpyrrolidone.
 6. The method of claim 1 wherein said chromatographiccolumn contains a molecular sieve adsorbent.